http://www.k-wave.org/forum/topic/absorption-coefficient-setting-of-different-mediums-in-a-ultrasound-simulation Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:50:39 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/absorption-coefficient-setting-of-different-mediums-in-a-ultrasound-simulation#post-5540 Wed, 22 Jun 2016 21:05:34 +0000 Bradley Treeby 5540@http://www.k-wave.org/forum/ <p>Hi Lirj,</p> <p>Both <code>medium.alpha_coeff</code> and <code>medium.BonA</code> can be defined as matrices in the same way as the sound speed and density. In the current version of k-Wave, <code>medium.alpha_power</code> must be a scalar because of the way acoustic absorption is encoded using a fractional Laplacian. </p> <p>If this is a problem, one option is to select a suitable scalar value for <code>medium.alpha_power</code>, and then perturb the values of <code>medium.alpha_coeff</code> so that you get the correct absorption in dB/cm at a particular reference frequency, i.e.,</p> <p><code>alpha_coeff_new = alpha_coeff * f_MHz ^ (y - y_ref);</code></p> <p>Here <code>alpha_coeff</code> and <code>y</code> are the actual power law values (e.g., from book values or measurements), <code>y_ref</code> is the reference value for <code>medium.alpha_power</code>, and <code>alpha_coeff_new</code> is the modified value to pass to k-Wave.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/absorption-coefficient-setting-of-different-mediums-in-a-ultrasound-simulation#post-5537 Wed, 22 Jun 2016 04:09:25 +0000 lirj 5537@http://www.k-wave.org/forum/ <p>Hi Dr. Treeby and Dr. Cox,<br /> My question is about the absorption coefficient setting of different mediums in a ultrasound simulation.<br /> We want to design a medium with different absorption coefficient in each position, in order to implement the simulation of real human body tissue. But we can only find the single setting of absorption coefficient from the K-WAVE toolbox. The related setting of the absorption coefficients are as follow:<br /> (1)medium.BonA, (2)medium.alpha_power, (3)medium.alpha_coeff.<br /> They all can only be set up for a scalar, but as we need, we need to set up the absorption coefficient of the medium like medium.sound_speed and medium.density.<br /> Thus, we want to know which variable can be set up to realize the function.<br /> We hope you can help us to solve this problem. Thank you!<br /> Best wishes!<br /> Lirj<br /> 2016.6.22 </p>